U.S. patent application number 10/083139 was filed with the patent office on 2002-06-27 for dual optical pickup head for accessing both dvd and cd disc.
This patent application is currently assigned to Acute Applied Technologies, Inc.. Invention is credited to Liu, Chin-Sung, Tsai, Shin-Ter.
Application Number | 20020080708 10/083139 |
Document ID | / |
Family ID | 23267649 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020080708 |
Kind Code |
A1 |
Liu, Chin-Sung ; et
al. |
June 27, 2002 |
Dual optical pickup head for accessing both DVD and CD disc
Abstract
A dual optical pick-up head for accessing CD, CD-R and DVD discs
is provided. The provided dual optical pick-up head uses an
objective lens and a laser source for DVD discs, and uses another
objective lens and another laser source for CD and CD-R discs.
Spirit of the invention is that both objective lenses are located
in the same lenses holder which connect to a guide rod, and the
lenses hold moves only along a radius of the corresponding disc.
Moreover, the laser beam produced by any laser source is
transmitted through corresponding objective lens to a disc, and the
reflected laser beam is transmitted through corresponding objective
lens to a PDIC and then a spot is formed and detected. Hence, the
location of each objective lens must satiate the requirement that
any spot that corresponds to a specific track of disc does not mix
with other spots that correspond to other track of disc.
Inventors: |
Liu, Chin-Sung; (Miao-Li,
TW) ; Tsai, Shin-Ter; (Taipei, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
|
Assignee: |
Acute Applied Technologies,
Inc.
Taipei City
TW
|
Family ID: |
23267649 |
Appl. No.: |
10/083139 |
Filed: |
February 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10083139 |
Feb 27, 2002 |
|
|
|
09325380 |
Jun 4, 1999 |
|
|
|
Current U.S.
Class: |
369/112.24 ;
G9B/7.102; G9B/7.12 |
Current CPC
Class: |
G11B 7/127 20130101;
G11B 7/13925 20130101; G11B 7/1374 20130101; G11B 2007/0006
20130101 |
Class at
Publication: |
369/112.24 |
International
Class: |
G11B 007/135 |
Claims
What is claimed is:
1. A dual optical pickup for accessing both DVD and CD disc,
comprising: an actuator, said actuator comprising a first objective
lens, a second objective lens, a objective lenses holder, and a
guide rod, wherein both said first objective lens and said second
objective lens are located inside said objective lenses holder,
said lenses holder being moved only parallel to an accessed disc by
using said guide rod; a first light assembly, said first light
assembly corresponding to a DVD disc; and a second light assembly,
said second light assembly corresponding to a CD disc, said second
light assembly being separated from said first light assembly.
2. The dual optical pickup head of claim 1, wherein both said first
objective lens and said second objective lens are fixed in said
objective lens holder.
3. The dual optical pickup head of claim 1, whereby the distance
between said first objective lens and said accessed disc is fixed
and the distance between said second objective lens and said
accessed disc is fixed.
4. The dual optical pickup head of claim 1, both said first light
assembly and said second light assembly being moved by said guide
rod.
5. The dual optical pickup head of claim 1, wherein said first
light assembly comprises a first laser source, a first beam
splitter, a first collimator and a first photo-detector integrated
circuit.
6. The dual optical pickup head of claim 5, wherein said first
laser source produces a first laser beam which transmits through
said first beam splitter, said first collimator, said first
objective lens in sequence and is focused in said DVD disc, then
said first laser beam being reflected by said DVD disc and
reflected said first laser beam being transmitted through said
first objective lens, said first collimator, said first beam
splitter in sequence and then being detected by said first
photo-detector integrated circuit.
7. The dual optical pickup head of claim 6, the wavelength of said
first laser beam being about 650 nm.
8. The dual optical pickup head of claim 1, the numerical aperture
of said first objective lens being about 0.60.
9. The dual optical pickup head of claim 6, wherein said first
laser beam is focused on said DVD disc and does not located in a
radius that is parallel to said guide rod.
10. The dual optical pickup head of claim 1, wherein said first
objective lens is moved between a first position and a second
position, said first position corresponding to the innermost track
of said DVD disc and said second position corresponding to the
outermost track of said DVD disc.
11. The dual optical pickup head of claim 1, wherein the spatial
relation between said objective lenses holder and said first light
assembly is varied while said objective lenses holder being moved
by said guide rod.
12. The dual optical pickup head of claim 6, wherein a projection
of said first laser beam which from a specific track of said DVD
disc should not be mixed with another projections of said first
laser beam which from any other track of said DVD disc.
13. The dual optical pickup head of claim 1, wherein said second
light assembly comprises a second laser source, a second beam
splitter, a second collimator and a second photo-detector
integrated circuit.
14. The dual optical pickup head of claim 13, wherein said second
laser source produces a second laser beam which transmits through
said second beam splitter, said second collimator, said second
objective lens in sequence and is focused in said CD disc, then
said second laser beam being reflected by said CD disc and
reflected said second laser beam being transmitted through said
second objective lens, said second collimator, said second beam
splitter in sequence and then being detected by said second
photo-detector integrated circuit.
15. The dual optical pickup head of claim 14, the wavelength of
said second laser beam being about 780 nm.
16. The dual optical pickup head of claim 1, the numerical aperture
of said second objective lens being about 0.4 to 0.5.
17. The dual optical pickup head of claim 14, wherein said second
laser beam is focused on said CD disc and does not located in a
radius that is parallel to said guide rod.
18. The dual optical pickup head of claim 14, wherein said second
objective lens moves between a second position and a second
position, said second position corresponding to the innermost track
of said CD disc and said second position corresponding to the
outermost track of said CD disc.
19. The dual optical pickup head of claim 1, wherein the spatial
relation between said objective lenses holder and said second light
assembly is varied while said objective lenses holder being moved
by said guide rod.
20. The dual optical pickup head of claim 19, wherein a projection
of said second laser beam which from a specific track of said CD
disc should not be mixed with another projections of said second
laser beam which from any other track of said CD disc.
Description
BACKGROUND OF THE INVENTION
[0001] This application is a continuous-in-part of the original
application Ser. No. as 09/325,380, which filed Jun. 4 1999.
FIELD OF THE INVENTION
[0002] The present invention relates to a dual optical pick-up head
that is capable of accessing both CD (compact disc) disc and DVD
(digital versatile disc) discs. More particularly, the present
invention relates to a dual optical pick-up head that not only
employs two objective lenses and one actuator but also rids the
requirement to switch position of objective lenses while different
discs are detected.
DESCRIPTION OF THE PRIOR ART
[0003] The DVD is an optical disc that is capable of recording a
large amount of digital information. Its recording scheme allows
the recording of digital information, such as video, computer
information or the like on a disc having the same diameter as the
CD, at a recording density of six to eight times as high as the CD.
No matter how, although the storage amount of DVD disc is larger
than CD disc, CD disc is more widespread used in many fields than
DVD disc. Thus, it is common commercial benefit that a DVD player
uses a dual optical pick-up head not only work with DVD discs but
also compatibly work with traditional CD discs.
[0004] Evidently, when picking up data from a DVD disc the dual
optical pick-up head works with a shorter focal length of objective
lens and a shorter wavelength laser beam. Moreover, when picking up
data from a CD disc the dual optical pick-up head works with a
larger focal lengths and a larger wavelength laser beam. Therefore,
the dual optical pick-up head should be capable to work with
different wavelength lasers and different focal-length objective
lenses.
[0005] In order to solve such a problem, one conventional method
uses two objective lenses for both DVD and CD separated where two
lenses are switched in accordance with the type of disc. Another
conventional method uses a correcting lens that is inserted into a
collimator portion, thereby correcting the aberration due to the
disc. The other conventional method uses a two-focal objective lens
such as holographic optical element (HOE) as an objective lens. A
further conventional method uses a liquid crystal (LCD) shutter to
modulate laser beam. Among these conventional methods, two methods
are more popular than others and are explained in posterior
paragraphs.
[0006] FIG. 1A and FIG. 1B show the mechanism of the dual optical
pick-up head with the usage of the two-focal point objective lens.
When CD disc 10 is accessed and 780-nm wavelength laser beam 11 is
incident, as shown in FIG. 1A, laser beam 11 transmits through
two-focal point objective lens 12 and is focused on CD disc 10.
Similarly, when DVD disc 13 is accessed and 650-nm wavelength laser
beam 14 is incident, as shown in FIG. 1B, laser beam 14 transmits
through two-focal point objective lens 12 and is focused on DVD
disc 13. Obviously, the optical performance of the two-focal point
objective lens 12 is complicated, and then the structure is complex
and the cost is expensive.
[0007] FIG. 2A and FIG. 2B show the mechanism of the dual optical
pick-up head with the usage two objective lenses. When CD disc 23
is accessed and 780-nm wavelength laser beam 24 is incident, as
shown in FIG. 2A, switching machine 22 puts CD objective lens 20
into path of 780-nm wavelength laser beam 24 and then 780-nm laser
wavelength beam 24 is focused on CD disc 23. Similarly, when DVD
disc 26 is accessed and 650-nm wavelength laser beam 25 is
incident, as shown in FIG. 2B, switching machine 22 put DVD
objective lens 21 into path of 650-nm wavelength laser beam 25 and
then 650-nm laser beam 25 is focused on DVD disc 26. Evidently, the
path of 780-nm wavelength laser beam 24 is equal to the path of
650-nm wavelength laser beam 25. Therefore, the positions of both
CD objective lenses 20 and DVD objective lens 21 are switched to
put required objective lens into the path of laser beam 24/25 while
different discs 23/26 is detected. Clearly, the case requires
complicated switching machine 22 that occupies a large space is
necessary to switch objective lens, and then it is not suitable for
a compact dual optical pick-up head.
[0008] Besides, in the method of using a LCD shutter, the
polarization of the laser beam and location of LCD must be properly
arranged, then the design is difficult to actualize. Furthermore,
the LCD needs additional driving circuit to maintain shutter
effect.
[0009] According to previous discussion, although several
conventional ways are presented to compass the subject, none of
them efficient and compact enough. Therefore, it is necessary to
develop an economical dual optical pick-up head for accessing both
CD and DVD discs.
SUMMARY OF THE INVENTION
[0010] One main object of the invention is to propose a dual
optical pick-up head that can detect DVD discs and CD discs with
one actuator and two objective lenses, especially to propose a dual
optical pick-up head without the necessarily of a switching machine
to switch these objective lenses while different discs are
detected.
[0011] In comparison with conventional dual optical pick-up head
with two objective lenses, a significant character of the proposed
dual optical pick-up head is that these objective lenses do not
have to switch their position while different discs are
detected.
[0012] Therefore, the position that laser beam project into disc
does not have to be located in a radius of disc that is parallel to
the guide rod. Hence, the location of these two objective lenses is
elastic and the configuration of the proposed dual optical pick-up
head is convertible. Besides, because there is no requirement to
use two-focal objective lens then the structure and fabrication of
the proposed dual optical pick-up head is simplified and
compact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Other objects, features, and advantages of the invention
will become apparent from the following detailed description of
preferred embodiments, with reference to the accompanying drawing
in which:
[0014] FIG. 1A and FIG. 1B illustrate an example of accessing both
CD and DVD discs according to a conventional technique;
[0015] FIG. 2A and FIG. 2B illustrate another example of accessing
both DVD and CD discs according to another conventional
technique;
[0016] FIG. 3A to FIG. 3D illustrate a preferred embodiment of the
invention; and
[0017] FIG. 4A to FIG. 4C illustrate how projection that laser beam
projects on photo-detector integrated circuit is varied.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] FIG. 3A to FIG. 3D schematically illustrate a preferred
embodiment of the invention. Obviously, the proposed dual optical
pick-up head at least has first objective lens 31, second objective
lens 32, objective lenses holder 33, guide rod 34, first light
assembly 35 and second light assembly 36.
[0019] The basic mechanism of the embodiment could be explained by
referring to FIG. 3A and FIG. 3B, where first objective lens 31 and
second objective lens 32 are located separated and are located with
lenses holder 33 Herein, it should be noted that the shape, the
distribution, and the connection of both these lenses 31/32 and
lenses holder 33 in FIG. 3A to FIG. 3B only is an example of this
invention, this invention is not limited by the details of these
figures.
[0020] When disc 30 is a DVD disc, first light beam 301 is
incident, as shown in FIG. 3A, and is transmits through first
objective lens 31 and focused on disc 30 (DVD disc). Similarly,
when disc 30 is a CD disc, second light beam 302 is incident, as
shown in FIG. 3B, and is transmits through second objective lens 32
and focused on disc 30 (CD disc). Indisputably, the invention uses
two separate objective lenses 31/32 to detect different kind disc
(DVD/CD) separately, thus, the structure and cost of each objective
lenses 31/32 are simply and cheap, and it is not necessary to
switch the location of the objective lenses 31/32 while different
kind discs 30 are detected. Further, owing to objective lenses
31/32 must be moved to detect different tracks of the detected disc
30, the invention only requires that the distances between each
objective lens 31/32 and disc 30 is fixed and requires that
objective lenses 31/32 essentially do not move along the tangent
direction of disc 30.
[0021] Both first objective lens 31 and second objective lens 32
are located in objective lenses holder 33 without any machine to
switch position of both objective lenses 31/32. Thus, both
objective lens 31/32 are moved with objective lenses holder 33,
neither first objective lens 31 not second objective lens 32 would
be moved inside objective lenses holder 33. In other words, both
objective lenses 31/32 are fixed in objective lenses holder 33.
Further, guide rod 34 is used to move objective lenses holder 33,
first light assembly 35 and second light assembly 36. However, it
should be emphasized that guide rod 34 is essentially parallel to
the detected disc 30, thus, the distance between both objective
lens 31.32 and disc 30 essential is fixed, and also is independent
on the movement of guide rod 34. Further, the number of guide rod
34 is not limited, the shape and the construction of guide rod 34
also are not limited.
[0022] Moreover, numerical aperture of first objective lens usually
is about 0.60 and numerical aperture of said second objective lens
usually is about 0.4 to 0.5. Besides, first light assembly 35
comprises first laser source 351, first beam splitter 352, first
collimator 353 and first photo detector integrated circuit (PDIC)
354. Second light assembly 36 comprises second laser source 361,
second beam splitter 362, second collimator 363 and second
photo-detector integrated circuit 364.
[0023] It should be noted that first objective lens 31 and first
light assembly 35 are used to access DVD disc; second objective
lens 32 and second light assembly 36 are used to access CD disc.
Moreover, in the embodiment, The position that first laser beam
project on disc 30 does not locate in a radius that is parallel to
guide rod 34, but the position that second laser beam project on
disc 30 does locate in a radius that is parallel to guide rod 34.
However, the invention never limits the project location of both
laser beams.
[0024] When disc 30 is a DVD disc, first laser source 351 produces
first laser beam which transmits through first beam splitter 352,
first collimator 353, first objective lens 31 in sequence and then
is focused on disc 30. Therewith first laser beam is reflected by
disc 30 and reflected first laser beam transmits through first
objective lens 31, first collimator 353, first beam splitter 352 in
sequence and then is detected by first photo detector integrated
circuit 354.
[0025] In comparison, if disc 30 is a CD disc, second laser source
361 produces second laser beam which transmits through second beam
splitter 362, second collimator 363, second objective lens 32 in
sequence and is focused on disc 30. Next, second laser beam is
reflected by disc 30 and reflected second laser beam transmits
through second objective lens 32, second collimator 363 and second
beam splitter 362 in sequence, and then is detected by second
photo-detector integrated circuit 364.
[0026] When different tracks of disc 30 are accessed, first
objective lens 31, first light assembly 35, second objective lens
32 and second light assembly 36 all are moved by guide rod 34,
where the moving direction is parallel to a radius of disc 30. FIG.
3C illustrates a specific case that the innermost track of disc is
accessed and FIG. 3D illustrates another specific case that the
outermost track of disc is accessed.
[0027] According to FIG. 3A through FIG. 3D, it is apparent that
second laser beam is always incident to second objective lens 32 by
a direction which is vertical to moving direction of objective
lenses holder 33. In comparison, first laser beam is incident to
first objective lens 31 by a direction that always is not parallel
to tangent direction of disc 30. Wherein, the degree of the angle
that between the direction that first laser beam is incident to
first objective lens 31, and the tangent direction of a point of
disc 30 that first laser beam is projected on it is varied.
Furthermore, the degree of the angle is gradually increased from
the innermost track of disc 30 to outermost track of disc 30. When
first objective lens 31 locates in a first position that
corresponds to the innermost track of disc 30, the degree of the
angle is {circumflex over (-)}1; when first objective lens 31
locates in a second position that corresponds to the outermost
track of disc 30, the degree of the angle is(D 2. Obviously, the
values of both {circumflex over (-)} 1 and {circumflex over (-)} 2
depend on the configuration of the dual optical pick-up head, and
should be carefully controlled to ensure the correct access of disc
30.
[0028] Because the reflected first laser beam does not be parallel
to tangent direction of disc 30 in first objective lens 31, the
projection that reflected first laser beam projects in first PDIC
352 is moveable. When different tracks of disc 30 are accessed, as
shown in FIG. 4B to FIB. 4C, not only first objective lens 31 is
moved in a interval that between the first position and the second
position, but also the angle that between the incident direction of
first laser beam and tangent direction of disc 30 is varied in
another interval that between {circumflex over (-)} 1 and
{circumflex over (-)} 2. Moreover, the variation of the angle is
proportional to the moving distance of first objective lens 31, and
the proportional relation comprises linear direct proportional
relation. Of course, projection 40 that first laser beam projects
on first PDIC 354 also is moved in a homologous range, and
homologous range also is proportional to the moving distance of
first objective lens 31. Thus, it is important that projection 40
of reflected first laser beam from any track should not be mix with
projections 40 of reflected first laser beam which from other
tracks, otherwise it is impossible to correctly access disc 30. In
other words, the value of {circumflex over (-)} 1 and value of
{circumflex over (-)} 2 must satisfy the requirement that
projection 40 of reflected first laser beam from any track should
not be mix with projections 40 of reflected first laser beam which
from other track.
[0029] FIG. 4A to FIG. 4C illustrate how projection 40 that first
laser beam projects in first photo detector integrated circuit 354
is varied. Moreover, in the provided embodiment the type of first
PDIC 354 is choused to such that there are four projections 40
correspond to one reflected first laser beam in first PDIC 354 at
same time. First, if location of first objective lens 31 is
corresponding to a radius of disc 30 which is parallel to moving
direction of objective lenses holder 33, as second objective lens
32 of the provided embodiment, then projection 40 are formed in
both x-axis and y-axis of first PDIC 354, as shown in FIG. 4A.
[0030] No matter how, in the provided embodiment first object lens
31 does not correspond to such a radius of disc 30, and the angle
that between the incident direction of first laser beam and the
tangent direction is varied in a range from {circumflex over (-)} 1
to {circumflex over (-)} 2. Thus, projection 40 of first laser beam
does not locate in both axes of first PDIC 354. When the innermost
track of disc is accessed, degree of the angle that between the
incident direction of first laser beam and the tangent direction is
{circumflex over (-)} 1, and projection 40 on first PDIC 354 is
counterclockwise moved with same angle {circumflex over (-)} 1, as
shown in FIG. 4B. Thereafter, when the outermost track is accessed,
degree of the angle that between the incident direction of first
laser beam and the tangent direction is {circumflex over (-)} 2,
and projection 40 of first laser beam is counterclockwise moved
with same angle {circumflex over (-)} 2, as shown in FIG. 4C.
[0031] Consequently, it is important that {circumflex over (-)} 2
is enough small such that projection 40 of first laser beam never
overrun either x-axis or y-axis of first PDIC 354 to insure that
projection 40 of first laser beam which from any specific track of
disc 30 is not confused with the projection of first laser beam
that from other track of disc 30.
[0032] Hence, the configuration of first laser source 351, first
beam splitter 352, first collimator 353, first photo-detector
integrated circuit 354 and first objective lens 31 is restricted by
the requirement that projection 40 of first laser beam which from a
specific track should not be mixed with projections 40 of first
laser beam which from any other tracks.
[0033] While in the previous embodiment the location of CD
objective lens (second objective lens 32) is corresponding to a
radius of disc 30 that always is parallel to guide rod 34 and the
location of DVD objective lens (first objective lens 31) is located
in another radius of disc 30 that always is not parallel to guide
rod 30. It is obviously that the mechanism of the invention is not
restricted by the provided embodiment. By contrast, both CD
objective lens (second objective lens 32) and DVD objective lens
(first objective lens 31) can be locate in any position. Therefore,
the only restriction of the structure of proposed dual optical
pick-up head is that both projection 40 of first laser beam form a
specific track of disc 30 can not be mixed with other projection 40
of first laser beam that form other track of disc 30. And
projection that second laser beam projects on second PDIC 364 form
a specific track of disc 30 also can not be mixed with other
projection of second laser beam that form other track of disc
30.
[0034] According to previous discussion, the location of first
objective lens 31, second objective lens 32, first light assembly
35 and second light assembly 36 are elastic, and then the
configuration of the proposed dual optical pick-up head is
convertible. Moreover, because there is no requirement to use
two-focal objective lens, the structure and fabrication of the
proposed dual optical pick-up head is simple and compact.
[0035] While the invention has been described by way of example and
in terms of preferred embodiment, the invention is not limited
there to. To the contrary, it is intended to cover various
modifications, procedures and products, and the scope of the
appended claims therefore should be accorded to the broadest
interpretation so as to encompass all such modifications and
similar arrangement, procedures and products.
* * * * *